A semiconductor device such as a conventional transistor or CMOS generally operates under a low-voltage (namely, a difference between a high-voltage signal level and a low-voltage signal level is 5 volts). Such low-voltage devices are characterized by high speed, low power consumption and low thermal dissipation. However, in design of a new generation of electronic products, a low-voltage transistor or CMOS level already does not occupy a dominant position of a logic circuit any longer. Accordingly, semiconductor device manufacturers advance semiconductor devices which can operate normally under a high-voltage (namely, a difference between a high-voltage signal level and a low-voltage signal level is greater than 5 volts). Although such high-voltage devices substantially meet application needs most of the time, it is disadvantageous in complicated design and manufacture, high costs, low speed, high power consumption, high thermal dissipation as compared with the low-voltage devices.
In another aspect, higher voltage (e.g., greater than 5 volts) is necessarily needed to drive a semiconductor device such as a high-voltage CMOS. This requires a driving stage to be constructed by a device which can bear a higher voltage, which surely enlarges a size of an integrated circuit, increases costs and meanwhile imposes higher requirements for thermal dissipation.